ATP depletion in rat cholangiocytes leads to marked internalization of membrane proteins
Article first published online: 30 DEC 2003
Copyright © 2000 American Association for the Study of Liver Diseases
Volume 31, Issue 5, pages 1045–1054, May 2000
How to Cite
Doctor, R. B., Dahl, R. H., Salter, K. D., Fouassier, L., Chen, J. and Fitz, J. G. (2000), ATP depletion in rat cholangiocytes leads to marked internalization of membrane proteins. Hepatology, 31: 1045–1054. doi: 10.1053/he.2000.5983
- Issue published online: 30 DEC 2003
- Article first published online: 30 DEC 2003
- Manuscript Accepted: 25 JAN 2000
- Manuscript Received: 8 NOV 1999
- Liver Scholar Award from the American Liver Foundation to R.B.D.
- INSERM Post-doctoral Fellowship Award to L.F.
- NIH to J.G.F.. Grant Number: R01 (DK 46082)
Intrahepatic bile ducts (BD) are a critical target of injury in the postischemic liver. Decreased vascular perfusion causes characteristic changes in the morphology of the ductular epithelia including a loss of secondary membrane structures and a decrease in plasma membrane surface area. Using adenosine triphosphate (ATP) depletion of cultured normal rat cholangiocytes (NRC) to model ischemic ducts, the present studies examined the fate of apical membrane proteins to determine whether membrane recycling might contribute to rapid functional recovery. Apical proteins, including γ-glutamyl transpeptidase (GGT), Na+-glucose cotransporter (SGLT1), and apically biotinylated proteins, were not shed into the luminal space during ATP depletion. Instead, labeling of surface proteins after ATP depletion showed a significant decrease in GGT and SGLT1, consistent with membrane internalization. Similarly, z-axis confocal microscopy of biotinylated apical proteins also showed protein internalization. During ATP recovery, SGLT1 transport activity remained profoundly depressed even after 24 hours of recovery, indicating that the function of the internalized apical proteins is not rapidly recovered. These studies suggest that the membrane internalization in ATP-depleted cholangiocytes is a unidirectional process that contributes to prolonged functional deficits after restoration of normal cellular ATP levels. This sustained decrease in transport capacity may contribute to the development of ductular injury in postischemic livers.